Synthesis, photophysical properties, and theoretical studies of hydride-alkynyl platinum(II) complexes. Molecular structures of [trans-PtH(C triple bond CC5H4N-2)(PPh3)2] and [Pt(η2-HC triple bond CCP

Article abstract of DOI:10.1021/om000143u

A series of mononuclear, [trans-PtH(C triple bond CR)(PPh₃)₂] (R = C₅H₄N-2 (1), (6-C triple bond CH)C₅H₃N-2 (2), C₆H₄NH₂-4 (3), (4-C triple bond CH)C_6<

Full text of DOI:10.1021/om000143u

Organometallics 2000, 19, 4385-4397
4385
Syn th esis, P h otop h ysica l P r op er ties, a n d Th eor etica l
Stu d ies of Hyd r id e-Alk yn yl P la tin u m (II) Com p lexes.
Molecu la r Str u ctu r es of [tr a n s-P tH(CtCC5H4N-2)(P P h 3)2]
a n d [P t(η2-HCtCCP h 2OH)(P P h 3)2]
Irene Ara,† J esu´s R. Berenguer,‡ Eduardo Eguiza´bal,‡ J uan Fornie´s,*,†
J ulio Go´mez,‡ Elena Lalinde,*,‡ and J ose´ M. Sa´ez-Rocher‡
Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-Consejo Superior de Investigaciones Cientı´ficas, 50009 Zaragoza,
Spain, and Departamento de Quı´mica-Grupo de Sı´ntesis Quı´mica de La Rioja, UA-CSIC
Universidad de La Rioja, 26001 Logron˜o, Spain
Received February 14, 2000
A series of mononuclear, [trans-PtH(CtCR)(PPh3)2] (R ) C5H4N-2 (1), (6-CtCH)C5H3N-2
(2), C6H4NH2-4 (3), (4-CtCH)C6H4 (4), (CH2)5CtCH (5)), and binuclear, [trans,trans-(PPh3)2-
HPt{µ-σ:σ-(CtC)2R}PtH(PPh3)2] (R ) C5H3N-2 (7), C6H4-1,4 (8)), hydride-alkynyl platinum
complexes has been prepared in good to moderate yields from the reactions of [trans-PtHCl-
(PPh3)2] with an excess of the corresponding alkyne in the presence of an excess of NEt2H
and from the reactions of [trans-PtHCl(PPh3)2] with 1 equiv of 2 or 4 in the presence of
diethylamine. An analogous reaction with HCtCCPh2OH leads to a mixture of [trans-PtH-
(CtCCPh2OH)(PPh3)2] (6a ) and [Pt(η2-HCtCCPh2OH)(PPh3)2] (6b). The binuclear diyne
complex [{(PPh3)2Pt}2{µ-η2:η2-(CtCH)2C6H4-1,4}] (9), prepared in high yield from [Pt(η2-
C2H4)(PPh3)2] and HCtCC6H4-1,4-CtCH (0.5 equiv), is also formed in the reaction leading
to 8. Complexes 5, 7, and 8 have been used as precursors to form the mixed-valence Pt(II)-
Pt(0) complexes 10-12. The spectroscopic characterization of the complexes and X-ray crystal
structure determination of 1 and 6b are included. Their absorption and some selected
emission spectra, examined on the basis of theoretical studies (EHMO), are also reported.
In tr od u ction
behaves differently toward platinum species containing
labile sites. Thus, it has been reported that this mono-
hydride reacts with [cis-Pt(C6F5)2(thf)2], yielding [trans-
(PPh3)(C6F5)Pt(µ-H)(µ-CtCPh)Pt(C6F5)(PPh3)],5 while
the analogous reaction with [cis-Pt(C6F5)2(CO)(thf)]
affords the µ-phenylethenylidene bridging complex
[cis,cis-(CO)(C6F5)2Pt(µ-CdCHPh)Pt(PPh3)2].6 In an at-
tempt to understand these reactions,7 we focused our
interest on new hydride-alkynyl platinum substrates.
Alkynyl complexes have been actively investigated
from a variety of viewpoints (structure, catalytic activ-
ity, development of functional materials, etc.),1 and in
recent years, there has been a growing interest in the
design of oligomeric and polymeric (including branched
systems) transition-metal complexes containing σ-bond-
ed acetylide units because of their significantly altered
physical properties compared to organic oligomers and
polymers.2 In this area, particular attention has been
paid to hydride-alkynyl and also to hydride-acetylene
complexes, since they are important reagents or inter-
mediates in many stoichiometric and catalytic pro-
cesses.3
(2) (a) Puddephatt, R. J . Chem. Commun. 1998, 1055. (b) Lang, H.
Angew. Chem., Int. Ed. Engl. 1994, 33, 547. (c) Bunz, U. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 968. (d) Zhu, Y.; Millet, D. B.; Wolf, M. O.;
Rettig, S. J . Organometallics 1999, 18, 1930 and references therein.
(e) Harriman, A.; Ziessel, R. J . Chem. Soc., Chem. Commun. 1996,
1707. (f) Antonelli, E.; Rossi, P.; Lo Sterzo, C.; Viola, E. J . Organomet.
Chem. 1999, 578, 210. (g) Whittall, I. R.; McDonagh, A. M.; Humphrey,
M. G. Adv. Organomet. Chem. 1999, 43, 349. (h) Leroux, F.; Stumpf,
R.; Fischer, H. Eur. J . Inorg. Chem. 1998, 1225. (i) Younus, M.; Long,
N. J .; Raithby, P. R.; Lewis, J . J . Organomet. Chem. 1998, 570, 55. (j)
Onitsuka, K.; Fujimoto, M.; Ohshiro, N.; Takahashi, S. Angew. Chem.,
Int. Ed. 1999, 38, 689. (k) Mu¨ller, C.; Whiteford, J . A.; Stang, P. J . J .
Am. Chem. Soc. 1998, 120, 9827. (l) Leininger, S.; Stang, P. J .; Huang,
S. Organometallics 1998, 17, 3981. (m) Younus, M.; Ko¨hler, A.; Cron,
S.; Chawdhury, N.; Al-Mandhary, M. R. A.; Khan, M. S.; Lewis, J .;
Long, N. J .; Friend, R. H.; Raithby, P. R. Angew. Chem., Int. Ed. Engl.
1998, 37, 3036. (n) Werner, H.; Bachmann, P.; Laubender, M.; Gevert,
O. Eur. J . Inorg. Chem. 1998, 1217. (o) Osawa, M.; Sonoki, H.; Hoshino,
M.; Wakatsuki, Y. Chem. Lett. 1998, 1081. (p) McDonagh, A. M.;
Humphrey, M. G.; Samoc, M.; Cuther-Davies, B.; Houbrechts, S.; Wada,
T.; Sasabe, H.; Persoons, A. J . Am. Chem. Soc. 1999, 121, 1405. (q)
Peters, T. B.; Bohling, J . C.; Arif, A. M.; Gladysz, J . A. Organometallics
1999, 18, 3261.
In the course of our studies designed to explore the
chemistry of alkynyl platinum complexes, we have
observed that the complex [trans-PtH(CtCPh)(PPh3)2]4
† Universidad de Zaragoza-Consejo Superior de Investigacions Ci-
ent´ıficas.
‡ UA-CSIC Universidad de La Rioja.
(1) (a) Nast, R. Coord. Chem. Rev. 1982, 47, 89. (b) Manna, J .; J ohn,
K. D.; Hopkins, M. D. Adv. Organomet. Chem. 1995, 38, 79. (c) Bruce,
M. I. Chem. Rev. 1998, 98, 2797. (d) Lang, H.; Ko¨hler, K.; Blau, S.
Coord. Chem. Rev. 1995, 143, 113. (e) Akita, M.; Moro-Oka, Y. Bull.
Chem. Soc. J pn. 1995, 68, 420. (f) Beck, W.; Niemer, B.; Wieser, M.
Angew. Chem., Int. Ed. Engl. 1993, 32, 923. (g) Fornie´s, J .; Lalinde,
E. J . Chem. Soc., Dalton Trans. 1996, 2587 and references therein.
10.1021/om000143u CCC: $19.00 © 2000 American Chemical Society
Publication on Web 09/21/2000

4386 Organometallics, Vol. 19, No. 21, 2000
Ara et al.
Although σ-bonded alkynyl and η2-bonded alkyne com-
plexes of platinum have been thoroughly investi-
gated,1a,b,g,2l,8,9 the number of reports about mixed
hydride-alkynylderivatives is very small4,5,10,11 and, as
far as we know, only two structures of mononuclear
complexes have been reported.4,10a
We report here the synthesis and characterization of
several new mononuclear (1-5, 6a ) and binuclear (7,
8) hydride-alkynyl platinum complexes, together with
the monoyne [Pt(η2-HCtCCPh2OH)(PPh3)2] (6b) and
diyne [{(PPh3)2Pt}2{µ-η2:η2-(CtCH)2C6H4-1,4}] (9) de-
rivatives, formed during the synthesis of 6a and 8,
respectively. The mixed-valence (Pt(II),Pt(0)) complexes
[{trans-(PPh3)2HPtCtCRCtCH}Pt(PPh3)2] (R ) C5H10
(10), C5H3N-2,6 (11), C6H4-1,4 (12)) and structural
studies for 1 and 6b are also reported. Finally, their
photophysical properties, examined on the basis of some
EHMO calculations, are also included.
Resu lts a n d Discu ssion
(i) Syn th esis a n d Ch a r a cter iza tion . A few hy-
dride-alkynyl mononuclear platinum complexes have
been prepared by different methods, such as addition
of the alkyne in the presence of base,4,10a chloride/
10g,h
hydride exchange using NaBH4
or NaCtCPh,10f or
oxidative addition to a platinum(0) precursor.10b,c The
purpose of this study was to synthesize several hydride-
alkynyl complexes starting from [trans-PtHCl(PPh3)2]
and suitable acetylene and diacetylene ligands (Schemes1
and 2).
The synthesis of [trans-PtH(CtCR)(PPh3)2] (R )
C5H4N-2 (1), (6-CtCH)C5H3N-2 (2), C6H4NH2-4 (3), (4-
CtCH)C6H4 (4), (CH2)5CtCH (5)) was based on a slight
modification of the method reported by Russo et al.,4,10a
by reacting [trans-PtHCl(PPh3)2] with an excess of the
corresponding acetylene in refluxing chloroform and in
the presence of NEt2H (path i, Scheme 1), to give the
final complexes in high yield (72-94%). The diethyl-
amine facilitates the proton elimination of the acetylene
as NEt2H2+Cl-, avoiding insertion reactions in the
Pt-H bond12 or the facile formation of chloroacetylides
by formal elimination of hydrogen,13 which had been
previously observed with HCtCPh and R-hydroxyacety-
lenes. The resulting pale orange solid obtained in the
reaction between [trans-PtHCl(PPh3)2] and p-diethynyl-
benzene (HCtCC6H4CtCH), even in the presence of an
excess (3.2 equiv) of this latter, was identified (31P and
1H NMR) as a mixture of the mononuclear 4 and the
dinuclear [trans,trans-(PPh3)2HPt{µ-σ:σ-(CtC)2-C6H4-
1,4}PtH(PPh3)2] (8) complexes (4:8 molar ratio 4:1).
Recrystallization of this solid from acetone/methanol
gave complex 4 as an orange powder (65% yield). In a
similar manner, the diplatinum complex 8 and the
analogous binuclear derivative [trans,trans-(PPh3)2HPt-
{µ-σ:σ-(CtC)2C5H3N-2,6}PtH(PPh3)2] (7) were pre-
pared in high yield (∼70%) by refluxing [trans-PtHCl-
(PPh3)2] for 1 h with 1 equiv of the precursor 4 or 2,
respectively, in CHCl3 in the presence of NEt2H (path
ii, Scheme 1). The synthetic approach based on the
direct condensation between the diterminal alkynes
with [trans-PtHCl(PPh3)2] gave worse results (path i,
Scheme 2). Thus, when 2,6-diethynylpyridine was treated
with 1 equiv of [trans-PtHCl(PPh3)2] under similar
conditions, the diplatinum complex 7 was formed along
with the mononuclear derivative 2 (7:2 ratio ∼1.4:1),
as confirmed by NMR spectroscopy after crystallization.
Subsequent recrystallization from CH2Cl2/MeOH gave
7 in very low yield (20%). The analogous reaction of
p-diethynylbenzene with 2 equiv of [trans-PtHCl(PPh3)2]
generated a mixture of 4 and 8 with the novel binuclear
diyne platinum(0) complex [{(PPh3)2Pt}2{µ-η2:η2-(Ct
CH)2C6H4-1,4}] (9), in which both alkyne linkages of the
p-diethynylbenzene are η2-bonded to two reduced “Pt0-
(PPh3)2” fragments. The yield of the three complexes
depends on the reaction times, the final solid obtained
after 75 min of reflux being a mixture of 4, 8, and 9 in
a 1:4.1:1.6 molar ratio. Recrystallization of this mixture
from CH2Cl2/acetone yields complex 8 in 18% yield.
(3) (a) Weber, L.; Barlmeyer, M.; Quasdorff, J .-M.; Sievers, H. L.;
Stammler, H.-G.; Neumann, B. Organometallics 1999, 18, 2497. (b)
J ime´nez, M. V.; Sola, E.; Mart´ınez, A. P.; Lahoz, F. J .; Oro, L. A.
Organometallics 1999, 18, 1125. (c) Huang, D.; Folting, K.; Caulton,
K. G. J . Am. Chem. Soc. 1999, 121, 10318. (d) Huang, T.-K.; Chi, Y.;
Peng, S.-M.; Lee, G.-H. Organometallics 1999, 18, 1675. (e) Bustelo,
E.; J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. Organometallics
1999, 18, 950. (f) Casey, C. P.; Brady, J . T. Organometallics 1998, 17,
4620. (g) Hamilton, D. H.; Shapley, J . R. Organometallics 1998, 17,
3087. (h) Torkelson, J . R.; McDonal, R.; Cowie, M. Organometallics
1999, 18, 4134.
(4) Furlani, A.; Licoccia, S.; Russo, M. V.; Chiesi-Villa, A.; Guastini,
C. J . Chem. Soc., Dalton Trans. 1982, 2449.
(5) Ara, I.; Falvello, L. R.; Fornie´s, J .; Lalinde, E.; Mart´ın, A.;
Mart´ınez, F.; Moreno, M. T. Organometallics 1997, 16, 5392.
(6) Ara, I.; Berenguer, J . R.; Fornie´s, J .; Lalinde, E.; Toma´s, M.
Organometallics 1996, 15, 1014.
(7) Berenguer, J . R.; Eguiza´bal, E.; Falvello, L. R.; Fornie´s, J .;
Lalinde, E.; Mart´ın, A. Organometallics 1999, 18, 1653.
(8) (a) Hartley, F. R. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press:
Oxford, U.K., 1982; Vol. 6. (b) Comprehensive Organometallic Chem-
istry II; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Puddephatt,
R. J ., Vol. Ed.; Pergamon Press: Oxford, U.K., 1995; Vol. 9, Chapters
8 and 9. (c) Pannell, K. H.; Crawford, G. M. J . Coord. Chem. 1973, 2,
251. (d) Nelson, J . H.; J onassen, H. B. Coord. Chem. Rev. 1971, 6, 27.
(9) (a) Wojcicki, A.; Schuchart, C. E. Coord. Chem. Rev. 1990, 105,
35. For recent works see: (b) AlQaisi, S. M.; Galat, K. J .; Chai, M.;
Ray, D. G.; Rinaldi, P. L.; Tessier, C. A.; Youngs, W. J . J . Am. Chem.
Soc. 1998, 110, 12149. (c) Falvello, L. R.; Fornie´s, J .; Go´mez, J .; Lalinde,
E.; Mart´ın, A.; Moreno, M. T.; Sacrista´n, J . Chem. Eur. J . 1999, 5,
474. (d) Wrackmeyer, B.; Sebald, A. J . Organomet. Chem. 1997, 544,
105. (e) Lewis, J .; Raithby, P. R.; Wong, W.-Y. J . Organomet. Chem.
1998, 556, 219. (f) Osella, D.; Gobetto, R.; Nervi, C.; Ravera, M.;
D’Amato, R.; Russo, M. V. Inorg. Chem. Commun. 1998, 239. (g) Pak,
J . J .; Weakley, T. J . R.; Haley, M. M. Organometallics 1997, 16, 4505.
(h) Falvello, L. R.; Ferna´ndez, S.; Fornie´s, J .; Lalinde, E.; Mart´ınez,
F.; Moreno, M. T. Organometallics 1997, 16, 1326. (i) Cucciolito, M.
E.; De Felice, V.; Orabona, I.; Ruffo, F. J . Chem. Soc., Dalton Trans.
1997, 1351. (j) Casey, Ch. P.; Chung, S.; Ha, Y.; Powell, D. R. Inorg.
Chim. Acta 1997, 265, 127. (k) Yamazaki, S.; Deeming, A. J .; Speel,
D. M. Organometallics 1998, 17, 775. (l) Shimada, S.; Tanaka, M.;
Honda, K. Inorg. Chim. Acta 1997, 265, 1. (m) Gerisch, M.; Heinemann,
F. W.; Bo¨gel, H.; Steinborn, D. J . Organomet. Chem. 1997, 548, 247.
(n) Braga, D.; Crepioni, F. Organometallics 1997, 16, 4910. (o) Su¨nkel,
K.; Birk, U.; Robl, C. Organometallics 1994, 13, 1679. (p) Klosin, J .;
Abboud, K. A.; J ones, W. M. Organometallics 1996, 15, 596. (q) Klosin,
J .; Abboud, K. A.; J ones, W. M. Organometallics 1995, 14, 2892. (r)
Albretch, K.; Hockless, D. C. R.; Ko¨nig, B.; Neumman, H.; Bennett,
M. A.; de Meijere, A. J . Chem. Soc., Chem. Commun. 1996, 543.
(10) (a) Russo, M. V.; Furlani, A.; Licoccia, S.; Paolesse, R.; Chiesi-
Villa, A.; Guastini, C. J . Organomet. Chem. 1994, 469, 245. (b) Hackett,
M.; Whitesides, G. M. J . Am. Chem. Soc. 1988, 110, 1449. (c) Hackett,
M.; Ibers, J . A.; J ernakoff, P.; Whitesides, G. M. J . Am. Chem. Soc.
1986, 108, 8094. (d) Nelson, J . H.; J onassen, H. B.; Roundhill, D. M.
Inorg. Chem. 1969, 8, 2591. (e) Glokling, F.; Hooton, K. A. J . Chem.
Soc. A 1967, 1066. (f) Tohda, Y.; Sonagoshira, K.; Hagihara, N. J .
Organomet. Chem. 1976, 110, C53. (g) Nast, R.; Moritz, J . J . Orga-
nomet. Chem. 1976, 117, 81. (h) Chisholm, M. H.; Couch, D. A. J . Chem.
Soc., Chem. Commun. 1974, 42.
(12) Furlani, A.; Russo, M. V.; Chiesi-Villa, A.; Gaetani Manfredotti,
A.; Guastini, C. J . Chem. Soc., Dalton Trans. 1977, 2154.
(13) (a) Furlani, A.; Licoccia, S.; Russo, M. V.; Guastini, C. J . Chem.
Soc., Dalton Trans. 1980, 1958. (b) Furlani, A.; Licoccia, S.; Russo, M.
V.; Guastini, C. Inorg. Chim. Acta 1979, 33, L125.
(11) (a) Langrick, C. R.; Pringle, P. G.; Shaw, B. L. J . Chem. Soc.,
Dalton Trans. 1985, 1015. (b) Ara, I.; Berenguer, J . R.; Fornie´s, J .;
Lalinde, E.; Moreno, M. T. Organometallics 1996, 15, 1820.

Hydride-Alkynyl Platinum(II) Complexes
Organometallics, Vol. 19, No. 21, 2000 4387
Sch em e 1
Sch em e 2
However, as expected, the binuclear diyne complex 9
was prepared in very high yield (83%) by treatment of
[Pt(η2-C2H4)(PPh3)2], suspended in acetone at room
temperature, with p-diethynylbenzene (molar ratio 1:2)
(ii, Scheme 2). Although the mechanism of the reductive
process in the above reaction is not clear, similar
intramolecular elimination of HCl on [trans-PtHCl-
(PPh3)2], yielding η2-bonded alkyne complexes [Pt(η2-
HCtCR)(PPh3)2], had been previously observed in
analogous reactions in the presence of hydrazine.12,14

4388 Organometallics, Vol. 19, No. 21, 2000
Ara et al.
Sch em e 3
As had been previously noted,4 the nature of the
substituent R of the alkyne molecule influences strongly
the course of these reactions. Thus, we have been unable
to prepare the mononuclear complex [trans-PtH(Ct
CCPh2OH)(PPh3)2] (6a ) in a pure form starting from
[trans-PtHCl(PPh3)2] and the R-hydroxyalkyne 1,1-
diphenyl-2-propyn-1-ol (HCtCCPh2OH). For different
reaction times and concentrations of the reactants, the
reaction always yielded a mixture of 6a (major compo-
nent) and the η2-bonded alkyne complex [Pt(η2-HCt
CCPh2OH)(PPh3)2] (6b) (minor component), which we
were not able to separate (path i, Scheme 2) in a
complete form. Complex 6b (described previously)10d
was prepared alternatively in 60% yield by treatment
of [Pt(η2-C2H4)(PPh3)2] with an equimolecular amount
of the propynol (HCtCCPh2OH) in acetone (path iii,
Scheme 2).
However, we have not succeeded in obtaining the
dihydride diplatinum compound [trans,trans-(PPh3)2-
HPt{CtC(CH2)5CtC}PtH(PPh3)2] under reaction con-
ditions similar to those used for 7 and 8, despite many
attempts. The free CtCH fragment on 5 seems to be
reluctant to further deprotonation, even in the presence
of stronger deprotonating agents such as n-BuLi and
KOt-Bu. Thus, in the reaction with n-BuLi, only the
starting materials 5 and [trans-PtHCl(PPh3)2] were
detected by NMR spectroscopy. However, the reaction
between 5 and [trans-PtHCl(PPh3)2] in the presence of
an excess of KO-t-Bu, in tetrahydrofuran, afforded a
mixture of products with the unexpected mixed-valence
Pt(II),Pt(0) complex [{trans-(PPh3)2HPtCtC(CH2)5Ct
CH}Pt(PPh3)2] (10) as the main component (path i,
Scheme 3). Although this complex can be isolated from
the mixture in a very low yield (∼15%), its preparation,
as expected, is more straightforward starting from the
platinum(0) precursor [Pt(η2-C2H4)(PPh3)2]. Thus (path
ii, Scheme 3), treatment of an acetone solution of
complex 5 with [Pt(η2-C2H4)(PPh3)2] (molar ratio 1:1) at
room temperature cleanly gave complex 10 as a beige
solid in a 87% yield. The synthesis of this complex
prompted us to explore the preparation of related
binuclear Pt(II),Pt(0) with CtCRCtCH (R ) C5H3N-2
and C6H4-1,4) as connecting bridging ligands. As ex-
pected, following a procedure similar to that used for
10, the reaction of the ethylene Pt(0) derivative [Pt(η2-
C2H4)(PPh3)2] with the mononuclear Pt(II) starting
materials [trans-PtH(CtCR)(PPh3)2] (R ) (6-CtCH)-
C5H3N-2 (2), (4-CtCH)C6H4 (4)) (path ii, Scheme 3) gave
the desired mixed-valence complexes [{trans-(PPh3)2-
HPtCtCRCtCH}Pt(PPh3)2] (R ) C5H3N-2,6 (11), C6H4-
1,4 (12)). Compounds 10-12 are rather stable, and no
isomerization toward the corresponding dihydride-
dialkynyl compounds (7 and 8) has been detected. In
fact, on standing in solution, complexes 10-12 only
evolve with loss of the Pt0(PPh3)2 fragment, regenerating
the corresponding mononuclear hydride-alkynyl de-
rivatives 5, 2, and 4, respectively. Isomerization from
an acetylene to an alkynide complex has been shown to
be an important step in polymerization reactions.
Although most of these processes proceed thermally,
some experimental studies on photoassisted C-C bond
cleavage of [Pt(PPh3)2(RCtCR)] to give [Pt(R)(CtCR)-
(PPh3)2] (R ) CN, COOMe) have also been reported.15
Nevertheless, photolysis of solutions of the alkyne
complexes 6b and 9 and the mixed-valence compound
12, in different solvents (CDCl3, CD3COCD3, and C6D6)
and under different conditions (125 or 400 W, Hg
lamps), only yielded complex mixtures in which the
expected hydride-alkynyl complexes 6a and 8 were not
detected.
1
The analytical and spectroscopic (IR and H, 31P{1H},
and 13C{1H} NMR) data are in agreement with the
formulation proposed for the new complexes (see Ex-
perimental Section for details). In addition, the molec-
ular structures of complexes 1 and 6b have been
determined by X-ray crystallography.
The most remarkable feature of the IR spectra of all
hydride derivatives is the presence of two absorptions
in the 2031-2121 cm-1 region which, on the basis of
previous assignments,1,4,7,10a can be attributed to ν(Ct
C) (high-wavenumber band 2099-2121 cm-1) and ν(Pt-
H) (2031-2073 cm-1) stretching vibrations, respectively.
Despite the presence of two CtC entities in the mono-
(15) (a) Baddley, W. H.; Panattoni, C.; Bandoli, G.; Clemente, D.
A.; Belluco, U. J . Am. Chem. Soc. 1971, 93, 5590. (b) Kubota, M.; Sly,
W. G.; Santasiero, B. D.; Clifton, M. S.; Kuo, L. Organometallics 1987,
6, 1257.
(14) Keubler, M.; Ugo, R.; Cemini, S.; Conti, F. J . Chem. Soc., Dalton
Trans. 1975, 1081.

Hydride-Alkynyl Platinum(II) Complexes
Organometallics, Vol. 19, No. 21, 2000 4389
nuclear complexes 2, 4, and 5, only one ν(CtC) absorp-
tion is observed (∼2100 cm-1, 2 and 4; 2121 cm-1, 5).
However, the terminal acetylenic protons are clearly
seen in their proton NMR spectra, appearing as a singlet
at ca. 3 ppm, except for complex 5, for which a broad
1
signal at 1.89 ppm is assigned on the basis of H-1H
1
COSY and H-13C correlation NMR spectra, to the Ct
CH proton. All complexes display the hydride resonance
(δ -6.54 to -6.11) as a triplet (2J P-H ) 14.3-15.5 Hz),
confirming the trans arrangement of the phosphine
ligands. Both the chemical shifts and the platinum
coupling constants (1J Pt-H ) 640-656 Hz) compare well
to those already reported for similar complexes4,7,10a,e
and are in the expected range observed for Pt(II)
hydrides having a C atom (alkynyl, alkyl, carbene) trans
to the hydride ligand.16 The presence of a singlet in their
31P{1H} NMR spectra (δ 26.33-29.34) and especially the
1
magnitude of J Pt-P (2907-2948 Hz) also confirms the
trans configuration of the ligands about platinum
centers.17 The alkynyl carbon resonances, in the 13C-
{1H} NMR spectra, fall in the range 107.17-124.84
ppm. These signals could not be located for all of the
complexes (see Experimental Section), while the char-
acteristic carbon signals for terminal CâtCRH acetylenic
units in monomers 2, 4, and 5 were found at lower
frequencies (δ 67.86-79.1, CR; δ 83.47-85.01, Câ).
F igu r e 1. View of the molecular structure of complex 1
(50% probability thermal ellipsoids), showing the atom-
numbering scheme. Hydrogen atoms, except H(1), have
been omitted for clarity.
Concerning the IR spectra of the alkyne derivatives,
Ta ble 1. Bon d Len gth s (Å) a n d An gles (d eg) for
Com p lexes 1 a n d 6b
both complexes 6b and 9 display one absorption due to
the ν(CtC) stretching vibration (1692 and 1688 cm-1
,
[trans-PtH(CtCC5H4N-2)(PPh3)2] (1)
respectively) in the region of coordinated triple
bonds.8,9i-r,10d,18,19 Although for complex 9 the terminal
tCH proton resonance is obscured by the phenyl
protons of PPh3 ligands, complex 6b exhibits a charac-
teristically low-field signal19for the alkyne hydrogen at
δ 6.46 (2J Pt-C ) 57.7 Hz) as a doublet of doublets, due
Pt(1)-C(1)
Pt(1)-P(2)
C(1)-C(2)
2.028(6)
2.2977(16)
1.202(8)
Pt(1)-P(1)
Pt(1)-H(1)
C(2)-C(3)
2.2718(16)
1.45(7)
1.446(8)
C(1)-Pt(1)-P(1)
P(1)-Pt(1)-H(1)
P(1)-Pt(1)-P(2)
94.54(18) C(1)-Pt(1)-P(2)
91.81(18)
84(3)
90(3)
P(2)-Pt(1)-H(1)
172.94(5)
C(1)-Pt(1)-H(1) 172(3)
C(1)-C(2)-C(3)
3
3
to the different couplings J Ptrans-H ) 22.7 and J Pcis-H
) 9.6 Hz. The proton resonance of the C6H4 ring in 9
appears as a singlet at low frequency (δ 6.59), probably
due to the shielding effect of PPh3.9l,p Both compounds
display a sharp ABX spin system (X ) 195Pt) in the 31P
NMR spectra consistent with in-plane coordination of
the alkyne unit and slow (relative to the NMR time
scale) rotation about the platinum-alkyne bond, and
in the 13C NMR spectra, the downfield complexation
shifts expected18,19 of the acetylenic HCtC carbon
resonances are observed (see Experimental Section for
details). Finally, in agreement with the formulation
given in Scheme 3, the mixed-valence complexes 10-
12 exhibit in their IR and 1H, 31P{1H}, and 13C{1H}
NMR spectra the expected spectroscopic data due to
both the Pt(0) and Pt(II) fragments (see Experimental
C(2)-C(1)-Pt(1) 175.6(7)
172.3(7)
[Pt(η2-HCtCCPh2OH)(PPh3)2] (6b)
Pt(1)-C(37)
Pt(1)-P(1)
C(37)-C(38)
2.045(5)
2.2836(12)
1.269(7)
Pt(1)-C(38)
Pt(1)-P(2)
C(38)-C(39)
2.075(5)
2.2787(13)
1.486(6)
C(37)-Pt(1)-C(38)
C(38)-Pt(1)-P(2)
35.9(2) C(37)-Pt(1)-P(1) 101.7(2)
112.5(2) P(1)-Pt(1)-P(2) 109.88(4)
C(37)-C(38)-C(39) 146.2(5)
Section). Again, the most remarkable feature of these
spectra is the absence of the terminal tCH proton
1
resonances in the H NMR spectra of 11 and 12, which
are obscured, as in 9, by the phenyl protons of PPh3
ligands.
(ii) Str u ctu r a l Stu d ies. The crystal structure of
[trans-PtH(CtCC5H4N-2)(PPh3)2] (1) contains discrete
molecules separated by normal distances. No significant
intermolecular contact between the pyridyl N and the
hydride ligand (6.042 Å) is found. The molecular struc-
ture is illustrated in Figure 1, and selected bond
parameters are collected in Table 1. In agreement with
our expectations based on NMR data, the molecule has
trans phosphine ligands. The acetylide group and the
hydrogen atom complete a distorted-square-planar ge-
ometry around the Pt center, with deviations from the
best least-squares plane ranging from 0.01 to 0.101 Å.
Despite the small steric demand of the hydride ligand,
the P(1)-Pt-P(2) axis is almost linear (172.94(5)°),
suggesting that the steric repulsion of the alkynyl
(16) (a) Michelin, R. A.; Ros, R. J . Chem. Soc.; Dalton Trans. 1989,
1149. (b) Crespo, M.; Sales, J .; Sola´ns, X.; Font-Altaba, M. J . Chem.
Soc., Dalton Trans. 1988, 1617. (c) Michelin, R. A.; Ros, R.; Guadalupi,
G.; Bombieri, G.; Benetollo, F.; Chapnis, G. Inorg. Chem. 1989, 28,
840. (d) Michelin, R. A.; Bertani, R.; Mozzon, M.; Zanotto, L.; Benetollo,
F.; Bombieri, G. Organometallics 1990, 9, 1449.
(17) (a) Pregosin, P. S.; Kunz, R. W. 31P and 13C NMR of Transition
Metal Phosphine Complexes; Springer: New York, 1997. (b) Falvello,
L. R.; Fornie´s, J .; Go´mez, J .; Lalinde, E.; Mart´ın, A.; Moreno, M. T.;
Sacrista´n, J . Chem. Eur. J . 1999, 5, 474.
(18) (a) Boag, N. M.; Green, M.; Grove, D. M.; Howard, J . A. K.;
Spencer, J . L.; Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1980, 2170.
(b) Heyns, J . B. B.; Stone, F. G. A. J . Organomet. Chem. 1978, 160,
337.
(19) (a) Nelson, J . H.; Reed, J . J . R.; J onassen, H. B. J . Organomet.
Chem. 1971, 29, 163. (b) Empsall, H. D.; Shaw, B. L.; Stringer, A. J .
J . Chem. Soc., Dalton Trans. 1976, 185.

4390 Organometallics, Vol. 19, No. 21, 2000
Ara et al.
Ta ble 2. UV/Vis Sp ectr a l Da ta in Ben zen e a t Room
Tem p er a tu r e (Con cen tr a tion ∼5 × 10-5 M)a
compd
λ )
max/nm (ꢀ/103 dm3 mol-1 cm-1
1
2
3
4
5
279 (21), 302 (16), 329 (9.7)
280 (22), 296 (15) (sh), 332 (13)
282 (29), 353 (8.9)
286 (24), 308 (23), 342 (19), 374 (7.4) (sh)
281 (25), 327 (3.3) (sh)
6a + 6b (5:1)
278 (11), 312 (2.0) (sh)
278 (11)
281 (42), 344 (19), 399 (5.7)
286 (43), 309 (29) (sh), 351 (23), 373 (35)
279 (36), 373 (20)
6b
7
8
9
10
11
12
279 (24), 323 (4.9) (sh)
280 (31), 338 (14)
280 (32), 307 (27), 343 (21), 375 (12)
[trans-PtHCl(PPh3)2] 279 (13)
HCtCC5H4N-2
282 (11)
(HCtC)2C5H3N-2,6
HCtCC6H4NH2-4
(HCtC)2C6H4-1,4
HCtC(CH2)5CtCH
HCtCCPh2OH
283 (41)
279 (26), 335 (1.5)
278 (16), 293 (4.8) (sh)
278 (3.2), 287 (2.2) (sh)
283 (7.7)
F igu r e 2. View of the molecular structure of complex 6b
(50% probability thermal ellipsoids), showing the atom-
numbering scheme. Hydrogen atoms have been omitted for
clarity.
a
For complexes 4 and 8, the absorption spectra were also taken
in acetone, the solvent dependence being minimal: 4, 327 (11) (sh),
339 (14), 371 (4.1) (sh); 8, 325 (12), 346 (15), 369 (22).
moiety (C(1)-Pt-P(1,2) angles 94.54(18), 91.81(18)°) is
probably relaxed, twisting the pyridyl substituent from
the platinum square plane (dihedral angle 116.12°). The
bond lengths Pt-P (2.2977(16), 2.2718(16) Å) and Pt-
σ-C (2.028(6) Å) and geometrical details of the alkynyl
fragment (CtC ) 1.202(8) Å, Pt-C(1)-C(2) ) 175.6(7)°,
C(1)-C(2)-C(3) ) 172.3(7)°) are in agreement with the
values expected for both types of ligands.
The hydride ligand is localized at a Pt-H distance
(1.45(7) Å) within comparable experimental error of
those reported for [trans-PtH(CtCEtMeOH)(PPh3)2]4
(1.98 Å) and other hydride platinum(II) complexes
F igu r e 3. Absorption spectra of complexes 4, 8, 9, and 12
in benzene at room temperature ([4] ) 5.9 × 10-5 M; [8] )
5.0 × 10-5 M; [9] ) 5.2 × 10-5 M; [12] ) 4.7 × 10-5 M).
such as [trans-PtH(COCH2CH2O)(PPh3)2] (1.72(8) Å),
[trans-PtH(CF3)(PPh3)2] (1.72(9) Å),20 [PtH(SB9H10)-
(PEt3)2] (1.66 Å),21 [cis-PtH(SiPh3)(PEt3)2] (1.75 Å),22
and [PtH(CH2CN)[C(NCH2CH2CH2)NH(C6H4-p-MeO)]-
(PPh3)] (1.61(4) Å).16d
C(sp) distances (2.045(5), 2.075(5) Å) being identical
within experimental error. However, the P(2)-Pt(1)-
C(38) angle is larger (112.5(2)°) than that of P(1)-Pt(1)-
C(37) (101.7(2)°). Similar differences have been observed
in [Pt(1-ethynylcyclohexanol)(PPh3)2].23 The length of
the CtC triple bond (1.269(7) Å) and the bending of the
alkyne fragment C(37)-C(38)-C(39) (146.2(5)°) lie well
within the range previously observed for this type of
compounds.
(iii) Absor p tion -Em ission Sp ectr a a n d Selected
EHMO Ca lcu la tion s. The data of the electronic ab-
sorption spectra of the new complexes (as well as for
the ligands), which were taken at room temperature in
benzene solutions, are summarized in Table 2. As
representative examples, the absorption spectra of 4,
8, 9, and 12 are shown in Figure 3. The ligands show a
strong absorption in the UV region (278-283 nm),
which can be ascribed to a π f π* transition. Compari-
son of the absorption spectra of the hydride-alkynyl
complexes with those of the alkyne entities and the
platinum precursor [trans-PtHCl(PPh3)2] (λmax 279 nm
with a tail extending to ∼330-340 nm) reveals the
appearance of new low-energy absorption bands being
more pronounced in the aryl derivatives. For the
The structure of the η2-alkyne complex 6b has also
been unambiguously established by X-ray crystallogra-
phy. The results are shown in Figure 2 and Table 1.
Despite the presence of an OH group, the complex
crystallizes as discrete molecules. No intermolecular
hydrogen bonding pattern has been observed, with the
shortest O‚‚‚O separation being approximately 9 Å. The
geometry at platinum is close to planar, the dihedral
angle between Pt(1)-P(1)-P(2) and Pt(1)-C(37)-C(38)
being 0.56(27)°. This angle is the usual one for η2-
acetylene Pt(0) complexes 8a-c,9i-p and can be compared
with those reported for [Pt(1-ethynylcyclohexanol)-
(PPh3)2] (6.7(8) and 7.2(7)°).23 Although the coordinated
alkyne is unsymmetrical, the coordination geometry at
the Pt center is essentially symmetrical, with both Pt-
(20) Michelin, R. A.; Ros, R.; Guadalupi, G.; Bombieri, G.; Benetollo,
F.; and Chapuis, G. Inorg. Chem. 1989, 28, 840.
(21) Kane, A. R.; Guggenberger, L. J .; Muetterties, E. L. J . Am.
Chem. Soc. 1970, 92, 2571.
(22) Koizumi, T.; Osakada, K.; Yamamoto, T. Organometallics 1997,
16, 6014.
(23) J agner, S.; Hazell, R. G.; Rasmussen, S. E. J . Chem. Soc., Dalton
Trans. 1976, 337.

Hydride-Alkynyl Platinum(II) Complexes
Organometallics, Vol. 19, No. 21, 2000 4391
Ta ble 3. Em ission a n d Excita tion Sp ectr a l Da ta in Ben zen e a t 77 K (Con cen tr a tion ∼5 × 10-3 M)
compd
πemmax/nm
πemxacx/nm
[trans-PtH{CtC(4-CtCH)C6H4}(PPh3)2] (4)
[trans,trans-(PPh3)2HPt{µ-σ:σ-(CtC)2C6H4-1,4}PtH(PPh3)2] (8)
[{(PPh3)2Pt}2{µ-η2:η2-(CtCH)2C6H4-1,4}] (9)
[{trans-(PPh3)2H-Pt-CtC(C6H4-1,4)CtCH}Pt(PPh3)2] (12)
[trans-PtH{CtC(6-CtCH)C5H3N-2}(PPh3)2] (2)
[trans,trans-(PPh3)2HPt{µ-σ:σ-(CtC)2C5H3N-2,6}PtH(PPh3)2] (7)
[{trans-(PPh3)2H-Pt-CtC-(C5H3N-2,6)-CtCH}Pt(PPh3)2] (11)
(HCtC)2C6H4-1,4
514, 544, 581
508, 543, 590
571, 598, 630, 663
544, 596
513
544
518, 542
404, 423, 466, 492
523
∼305, 383
302, 366, 387
330, 397
391
358, 391, 432
367, 393, 455
371
271, 337, 355, 369
271
(HCtC)2C5H3N-2,6
complexes [trans-PtH{CtC(CH2)5CtCH}(PPh3)2] (5)
and [trans-PtH(CtCCPh2OH)(PPh3)2] (6a ) (5:1 mixture
of 6a ,b) the absorption maxima (λmax) occurs only as a
shoulder at 327 and 312 nm, respectively. The lowest
absorption band shifts to lower energies in the remain-
ing mononuclear complexes, following the order 1 (329
nm) < 2, (332 nm) < 3 (353 nm) < 4 (374 nm). On the
basis of previous assignments and theoretical and
photoelectron studies24 on neutral bis(alkynyl)platinum
complexes, the moderately intense low-energy band is
decreasing the HOMO-LUMO gap, explaining the red
shift observed in 4.
The introduction of the platinum(0) fragment Pt-
(PPh3)2 on the terminal acetylenic fragment in the
mononuclear complexes 2, 4, and 5 causes only minor
modifications in their spectra, suggesting very little
electronic communication between the platinum centers.
For the resulting complexes 10-12, the observed low-
energy absorptions (λ, nm (ꢀ, dm3 mol-1 cm-1): 323 (4.9
× 103), 10; 338 (14 × 103), 11. 375 (12 × 103), 12) are
ascribed to Pt(0)-to-alkyne entity charge transfer on
basis of EHMO analyses (see below).
In the last few years, the search for novel luminescent
materials has attracted considerable attention.27 In this
area in particular, since the first observation of lumi-
nescence on a platinum compound containing alkynyl
ligands,28 a series of platinum alkynyl complexes have
been described to exhibit a rich and remarkable
photoluminescence.24d,25c,27a,29-32 The luminescence prop-
erties of mononuclear (2, 4) and binuclear (7-9, 11, 12)
compounds have been examined. They are strongly
emissive in frozen (77 K) benzene solutions, whereas
the corresponding free diynes emit weakly (Table 3 and
Figure 4 for 4, 8, 9, and 12). Vibronically structured
emission bands are detected for 4, 8, 9, and 12 at λmax
508-571 nm, which are slightly red-shifted relative to
the free diyne HCtCC6H4-1,4-CtCH. As can be ob-
served in Figure 4, the influence of the second Pt(II)
center in going from 4 to 8 has little effect on the
emission maximum. However, a clear red shift is
observed on going from the Pt(II)-Pt(II) compound 8
1
tentatively assigned as MLCT π f π*;2l,p,9e,g,24a,d,25 the
HOMO is of Pt-C π-antibonding character, resulting
from a metal d and acetylide π-fragment interaction,
and the LUMO mainly has a ligand π*-orbital character.
The tendency observed can be rationalized on the basis
of previous theoretical results, which show that aryl
substituents allow further electronic mixing with either
π or π* levels, producing a large decrease in the energy
of the acetylenic π* orbitals and a somewhat smaller
increase in the energy of metal-acetylene bonding,
reducing the HOMO-LUMO gap.24c,e
It is worthy of note that the introduction of a second
platinum fragment in the 2,6-bis(ethynyl)pyridine ligand
clearly shifts this absorption toward longer wavelengths
(λmax 399 nm for 7 vs 332 nm for 2), reflecting a higher
degree of conjugation, which probably reduces the
energy gap between the highest occupied and lowest
unoccupied molecular orbitals (HOMO and LUMO). For
the mononuclear derivative 4, the absorptions at 342
nm (ꢀ ) 19 × 103 dm3 mol-1 cm-1) and 374 nm (ꢀ ) 7.4
× 103 dm3 mol-1 cm-1) are tentatively assigned to spin-
3
allowed and spin-forbidden (1MLCT and MLCT π f π*)
(27) For some rewievs see: (a) Yam, V. W.-W.; Lo, K. K.-W.; Wong,
K. M.-C. J . Organomet. Chem. 1999, 578, 3. (b) Chan, C. W.; Cheng,
L. K.; Che, C. M. Coord. Chem. Rev. 1994, 132, 87. (c) Yam, V. W. W.;
Lo, K. K.-W. Chem. Soc. Rev. 1999, 28, 323. (d) Ford, P. C.; Vogler, A.
Acc. Chem. Res. 1993, 26, 220.
(28) (a) Baralt, E.; Boudreaux, E. A.; Demas, J . N.; Lenhert, P. G.;
Lukehart, C. M.; McPhail, A. T.; McPhail, D. R.; Myers, J . B.;
Sacksteder, L.; True, W. R. Organometallics 1989, 8, 2417. (b)
Sacksteder, L.; Baralt, E.; DeGraff, B. A.; Lukehart, C. M.; Demas, J .
N. Inorg. Chem. 1991, 30, 3955.
transitions, respectively. This assignment is in agree-
ment with a red shift on going from 4 to 8 (342 vs 373
nm) and is in line with the value of λmax absorption
recently reported for [trans-PtPh(CtC-p-C6H4CtCH)-
(PEt3)2] (327 nm, log ꢀ 4.58).26 The presence of a hydride
ligand trans to the alkynyl, instead of the Ph group,
should increase the electron density on the platinum
center, raising the energy of the HOMO and, thereby,
(29) Ng, Y.-Y.; Che, Ch.-M.; Peng, S.-M. New J . Chem. 1996, 20,
781.
(30) (a) Lewis, J .; Khan, M. S.; Kakkar, A. K.; J ohnson, B. F. G.;
Marder, T. B.; Fyfe, H. B.; Wittmann, F.; Friend, R. H.; Dray, A. E. J .
Organomet. Chem. 1992, 425, 165. (b) Chawdhury, N.; Ko¨hler, A.;
Friend, R. H.; Younus, M.; Long, N. J .; Raithby, P. R.; Lewis, J .
Macromolecules 1998, 31, 722. (c) Chawdhury, N.; Ko¨hler, A.; Friend,
R. H.; Wong, W.-Y.; Lewis, J .; Younus, M.; Raithby, P. R.; Corcoran,
T. C.; Al-Mandhary, M. R. A.; Khan, M. S. J . Chem. Phys. 1999, 110,
4963.
(31) (a) Yam, W. W. W.; Chan, L. P.; Lai, T. F. Organometallics 1993,
12, 2197. (b) Yam, W. W. W.; Yeung, P. K. Y.; Chan, L. P.; Kwok, W.
M.; Phillips, D. L.; Yu, K. L.; Wong, R. W. K.; Yan, H.; Meng, Q. J .
Organometallics 1998, 17, 2590.
(32) (a) Ara, I.; Berenguer, J . R.; Fornie´s, J .; Go´mez, J .; Lalinde,
E.; Merino, R. I. Inorg. Chem. 1997, 36, 6461. (b) Ara, I.; Fornie´s, J .;
Go´mez, J .; Lalinde, E.; Merino, R. I.; Moreno, M. T. Inorg. Chem.
Commun. 1999, 2, 62. (c) Chartmant, J . P. H.; Fornie´s, J .; Go´mez, J .;
Lalinde, E.; Merino, R. I.; Moreno, M. T.; Orpen, A. G. Organometallics
1999, 18, 3353.
(24) (a) Masai, H.; Sonogashira, K.; Hagihara, N. Bull. Chem. Soc.
J pn. 1971, 44, 2226. (b) Louwen, J . N.; Hengelmolen, R.; Grove, D.
M.; Oskam, A. Organometallics 1984, 3, 908. (c) Frapper, G.; Kertesz,
M. Inorg. Chem. 1993, 32, 732. (d) Yip, H.-K.; Lin, H.-H.; Wang, Y.;
Che, C. M. J . Chem. Soc., Dalton Trans. 1993, 2939. (e) Khan, M. S.;
Kakkar, A. K.; Ingham, S. L.; Raithby, P. R.; Lewis, J .; Spencer, B.;
Wittmann, F.; Friend, R. H. J . Organomet. Chem. 1994, 472, 247. (f)
Long, N. J .; Mart´ın, A. J .; Vilar, R.; White, A. J . P.; Williams, D. J .;
Younus, M. Organometallics 1999, 18, 4261.
(25) For some additional examples see: (a) Lewis, J .; Long, N. J .;
Raithby, P. R.; Shields, G. P.; Wong, W.-Y.; Younus, M. J . Chem. Soc.,
Dalton Trans. 1997, 4283. (b) Faust, R.; Diederich, F.; Gramlich, V.;
Seiler, P. Chem. Eur. J . 1995, 1, 111. (c) Sacksteder, L.; Baralt, E.;
DeGraff, B. A.; Lukehart, C. M.; Demas, J . N. Inorg. Chem. 1991, 30,
2468.
(26) Younus, M.; Long, N. J .; Raithby, P. R.; Lewis, J . J . Organomet.
Chem. 1998, 570, 55.

4392 Organometallics, Vol. 19, No. 21, 2000
Ara et al.
For complexes A and B, the calculations were per-
formed in C2v and D2h symmetries, respectively. The
coordinate system chosen is shown in Figure 5. The
results of these studies for both complexes, which
provide a qualitative description of the frontier orbitals,
are collected in Table 4 and an schematic view of the
HOMO and LUMO for the diplatinum complex B is
given in Figure 5. In agreement with previous theoreti-
cal and photoelectronic studies,24 the interaction be-
tween the Pt centers and the alkynyl ligand is of filled-
filled type with Pt-π* back-bonding being of minimal
importance. In both, the HOMO arises from a π interac-
tion between platinum orbitals (symmetry 2b2 (A) and
4b2g (B) for PtH(PH3)2 fragments) with the π system of
the acetylenic fragment (4b2 for A and 2b2g for B)
having, as shown in Figure 5, a Pt-CR antibonding and
CtC bonding nature (6b2, A; 6b2g, B). The LUMO in
both compounds is mainly located in the alkynyl system
and is rather similar to that obtained for HCtCC6H4-
1,4-CtCH.24c The participation of the Pt atoms (a mixed
pz-dxz orbital) is very small (3%, A; 6%, B). Thus, on
the basis of these results, it seems appropriate to assign
a considerable character of MLCT to the transitions
measured in the absorption and emission spectra of the
hydride alkynyl complexes.
F igu r e 4. Emission spectra of complexes 4, 8, 9, and 12
in benzene at 77 K (λex ) 383 nm for 4, 387 nm for 8, 397
nm for 9, and 391 nm for 12; concentration ∼5 × 10-3 M).
(λmax 508 nm) to the diyne isomer Pt(0)-Pt(0) 9 (571
nm). For 9, the vibrational spacings of ∼790 and 1640
cm-1 observed correlate well with phenyl-ring skeletal
and alkyne CtC (ν(CtC) for 9 1688 cm-1) stretching
vibrations. Vibrational peaks for 4 (at 1073, 1171 cm-1
)
and 8 (at 1269, 1467 cm-1) may be due to C-H bends
and ring C-C stretches, indicating distortion of the
central phenylene ring in the excited state. The third
isomer, the alkynyl-alkyne mixed-valence, Pt(II)-Pt(0)
derivative 12, exhibits an structured band with a λmax
value (544 nm) between those found for 8 and 9. In this
case, the vibrational progression of 1604 cm-1 observed
compares favorably with the ground-state ν(CtC) of the
complexed η2-alkyne Pt(0) fragment, suggesting that the
emission of this complex has to be associated with this
entity. An extended Hu¨ckel calculation on [{trans-
(PH3)2HPt(CtCC6H4-1,4-CtCH)}Pt0(PH3)2] (D) as a
model complex also predicts that the HOMO is mainly
located on the Pt(0) fragment (see below). The emission
The results of the EHMO calculations on the elec-
tronic structures of the model complexes [{Pt0(PH3)2}2-
(HCtCC6H4-1,4-CtCH)] (C) and [{trans-(PH3)2HPt(Ct
CC6H4-1,4-CtCH)}Pt0(PH3)2] (D) (Table 4 and Figure
6 for D) confirm that, not only in C but also in the
mixed-valence D, the HOMO has a significant partici-
pation of the platinum(0) atoms. Thus, in both C and
D complexes, the lowest unoccupied molecular orbital
(LUMO) is, as in compounds A and B, mainly located
in the hydrocarbon fragment (in this case the diyne
fragment). It is also labeled as π* and shows a consider-
able delocalization through the phenylene bridge. How-
ever, their HOMO possesses approximately half-and-
half metal-carbon character. As can be observed in
Figure 6, which shows a schematic representation of the
contribution to the HOMO in D, in this case the
participation of the metals is located on Pt(0) and has
a notable d character. The remaining participation is
delocalized along the whole carbon skeleton with a very
small contribution of the Pt(II) center. The HOMO has
σ* antibonding nature relative to the Pt(0) atom because
it arises from a filled-filled type interaction between
of complexes formed from 2,6-diethynylpyridine (λmax
,
nm: 513, 2, Pt(II); 544, 7, Pt(II)-Pt(II); 518, 542, 11,
Pt(II)-Pt(0)) shows broad features (with a poorly re-
solved vibronic structure for 11) similar to that observed
for the free diyne (see Table 3). The most remarkable
difference is found in their excitation spectra; free diyne
shows one excitation maximum at 271 nm, whereas 2
and 7 exhibit three distinctive features (358, 391, 432
cm-1, 2; 367, 393, 455 cm-1, 7), a phenomenon which
had been previously observed in bis(alkynyl) platinum
complexes, for which the emissions have been associated
with MLCT excited states.24d,25c The excitation spectrum
of complex 11 is different from those observed for 2 and
7, showing only an excitation maximum in the low-
energy region at 371 nm. Therefore, the emission for
this complex, as the emission for 12, is thought to be
largely localized on the low-valence fragment.
2
fragment A and a mixed (dxz-dz -px-pz) platinum
orbital. In C, the HOMO is symmetrical with the
participation of both Pt centers (25% each) and of all
diyne fragments. In both, since the Pt(0) d character is
remarkable in the HOMO, and the LUMO is mainly
localized in the π* system, the corresponding electronic
transitions are also essentially metal-to-ligand charge
transfer (MLCT). Similar assignments had been previ-
ously reported for more simple [Pt(RCtCR)(PPh3)2]
complexes.34
To clarify the nature of these transitions, simple
extended Hu¨ckel calculations33 were performed on
[trans-PtH(CtCC6H4-1,4-CtCH)(PH3)2] (A) and [trans,-
trans-(PH3)2HPt(CtCC6H4-1,4-CtC)PtH(PH3)2] (B) as
model complexes for hydride alkynyl compounds 4 and
8 and on [{Pt0(PH3)2}2(HCtCC6H4-1,4-CtCH)] (C) and
[{trans-(PH3)2HPt(CtCC6H4-1,4-CtCH)}Pt0(PH3)2] (D)
as models for 9 and 12.
(iv) Con clu sion s. In summary, several mononuclear
(1-6) and binuclear (7, 8) hydride-alkynyl platinum-
(II) complexes have been reported, together with some
Pt(0)-diyne (9) and mixed Pt(II)-Pt(0) hydrid--alky-
nyl-alkyne (10-12) binuclear derivatives. Their ab-
(34) Koie, Y.; Shinoda, S.; Saito, Y. J . Chem. Soc., Dalton Trans.
1981, 1082.
(33) Mealli, C.; Proserpio, D. M. J . Chem. Educ. 1990, 67, 3399.

Hydride-Alkynyl Platinum(II) Complexes
Organometallics, Vol. 19, No. 21, 2000 4393
F igu r e 5. Representation of the most important contributions to the LUMO (a) and HOMO (b) in [trans,trans-(PH3)2-
HPt(CtCC6H4-1,4-CtC)PtH(PH3)2] (B).
Ta ble 4. Su m m a r y of Com p u ta tion a l Resu lts for [tr a n s-P tH(CtC-C6H4-1,4-C≡CH)(P H3)2] (A),
[tr a n s,tr a n s-(P H3)2HP t(CtCC6H4-1,4-CtC)P tH(P H3)2] (B), [{P t0(P H3)2}2(HCtCC6H4-1,4-CtCH)] (C), a n d
[{tr a n s-(P H3)2HP t(CtCC6H4-1,4-CtCH)}P t0(P H3)2] (D)
compd
HOMO [E/eV]
LUMO [E/eV]
A
B
C
D
π(CtCC6H4-1,4-CtC)-π*(Pt) (29% dxz) [-12.04]
π*(CtCC6H4-1,4-CtC) [-9.14]
π*(Pt) (16%)-π(CtCC6H4-1,4-CtC)-π*(Pt) (16% dxz) [-11.92]
σ*(Pt0) (25%)-π(CtCC6H4-1,4-CtC)-σ*(Pt0) (25%) [-11.56]
π*(Pt) (3%)-π(CtC-C6H4-1,4-CtC)-σ*Pt0(60%) [-11.65]
π*(CtC-C6H4-1,4-CtC) [-9.12]
π*Pt0 (5%)-π*(CtCC6H4-1,4-CtC)-π*(Pt0) (5%) [-8.50]
π*(Pt) (4%)-π*(CtCC6H4-1,4-CtC)-π*(Pt0) (4%) [-8.86]
F igu r e 6. Schematic representation of the calculated LUMO (a) and HOMO (b) in [{trans-(PH3)2HPt(CtCC6H4-1,4-Ct
CH)}Pt0(PH3)2] (D).
sorption and some emission spectra have been examined
and analyzed on the basis of EHMO calculations on
[trans-PtH(CtCC6H4-1,4-CtCH)(PH3)2] (A) and the
isomeric compounds [trans,trans-(PH3)2HPt(CtCC6H4-

4394 Organometallics, Vol. 19, No. 21, 2000
Ara et al.
(CtC) 2109 (s); ν(Pt-H) 2044 (m). 1H NMR (CDCl3, δ; J in
Hz): 8.28 (d, J H-H ) 4.2, H6); 7.71 (m, o-H, Ph, PPh3); 7.35
(m, m-H and p-H, Ph, PPh3); 7.23 (t, J H-H ) 7.6, H4); 6.82 (m,
2
1
H5); 6.42 (d, J H-H ) 7.8, H3); -6.30 (t, J P-H ) 15.5; J Pt-H
)
645, Pt-H) (based on H-1H COSY NMR spectrum). 13C NMR
1
(CDCl3, δ; J in Hz): 148.52 (s, C6); 147.25 (s, J Pt-C ) 23, C2);
3
1
3
134.60 (s, o-C, Ph, PPh3); 133.13 (t, J P-C + J P-C ) 54, i-C,
Ph, PPh3); 130.14 (s, p-C, Ph, PPh3); 127.99 (s, m-C, Ph, PPh3
and probably C4 or C5); 126.04 (s, J Pt-C ) 6.4, C3); 118.95 (s,
4
C4 or C5); 115.01 (s, J Pt-C ) 236, Câ); CR is not observed. 31P
2
â
1
NMR (CDCl3, δ; J in Hz): 26.50 (s, J Pt-P ) 2917).
F igu r e 7.
Syn th esis of [tr a n s-P tH{CtC(6-CtCH)C5H3N-2}(P P h 3)2]
(2). Complex 2 was prepared as a beige solid following a
procedure identical with that described for 1: 0.40 g (0.53
mmol) of [trans-PtHCl(PPh3)2], 0.14 g (1.10 mmol) of 2,6-bis-
(ethynyl)pyridine, and 1 mL of NEt2H were used with a
refluxing time of 2.5 h. Yield: 94%.
1,4-CtC)PtH(PH3)2] (B), [{Pt0(PH3)2}2(HCtCC6H4-1,4-
CtCH)] (C), and [{trans-(PH3)2HPt(CtCC6H4-1,4-Ct
CH)}Pt0(PH3)2] (D) as model complexes.
The results suggest that (i) the LUMO is always
centered on the π* skeleton carbon, (ii) the HOMO in
the hydride-alkynyl Pt(II) compounds A and B is a π
orbital with a notable Pt d orbital and a Pt-C anti-
bonding character, and (iii) the HOMO in C and D
consists of the valence d orbitals of Pt(0).
It is worth to note that compounds 10-12 which are
the first reported hydride-alkynyl-alkyne Pt(II)-Pt-
(0) mixed-valence derivatives, are rather stable and no
isomerization toward the corresponding dihydride-
dialkynyl compounds (7 and 8) has been detected.
Data for 2 are as follows. Anal. Calcd for C45H35NP2Pt: C,
63.82; H, 4.16; N, 1.65. Found: C, 63.69; H, 3.87; N, 1.68. MS:
m/z 847 [M + H]+ 20%; 719 [Pt(PPh3)2]+ 100%. IR (cm-1): ν-
1
(CtC) 2100 (s); ν(Pt-H) ∼2040 (sh). H NMR (CDCl3, δ; J in
Hz): 7.69 (m, o-H, Ph, PPh3); 7.35 (m, m-H and p-H, Ph, PPh3);
7.19 (t, J H-H ) 7.7, H4); 7.04 (d, J H-H ) 7.5, H5); 6.40 (d, J H-H
2
1
) 7.8, H3); 2.98 (s, CtCH); -6.27 (t, J P-H ) 14.3; J Pt-H
)
)
646, Pt-H). 13C NMR (CDCl3, δ; J in Hz): 147.47 (s, J Pt-C
3
24, C2); 140.98 (s, C6); 134.74 (s, C4); 134.60 (s br, o-C, Ph,
PPh3); 133.09 (m, i-C, Ph, PPh3); 130.15 (s, p-C, Ph, PPh3);
128.00 (s, m-C, Ph, PPh3); 125.90 (s, J Pt-C ) 7.1, C3); 122.90
4
(s, C5); 114.34 (s, J Pt-C ) 236, Câ); CR is not observed; 83.47
2
â
(s, Câ, CâtCRH); 75.39 (s, CR, CâtCRH). 31P NMR (CDCl3, δ; J
Exp er im en ta l Section
1
in Hz): 26.52 (s, J Pt-P ) 2914).
1H, 13C, and 31P NMR spectra were recorded at 20 °C on a
Bruker ARX-300 spectrometer. Chemical shifts are reported
in ppm relative to external standards (SiMe4 and 88% H3PO4),
and coupling constants are given in Hz. The NMR spectral
assignments follow the numbering scheme shown in Figure
7. Infrared spectra were recorded with Perkin-Elmer 883 or
Spectrum 1000 spectrometers as Nujol mulls between poly-
ethylene sheets (1-3, 6a ,b, 9) or as pellets in KBr (4, 5, 7, 8,
10-12). C, H, and N analyses were carried out with a Perkin-
Elmer 240 microanalyzer or a Perkin-Elmer 2400 CHNS/O
analyzer. Mass spectra were obtained in a VG Autospec
double-focusing mass spectrometer operating in the FAB+
mode, except for complexes 9-11 (HP-5989B mass spectrom-
eter using the ES(+) technique). The synthesis and spectro-
scopic and analytical data of 1 have been previously reported
by us.7 The syntheses of complexes 6b and 9-12 were carried
out under a nitrogen atmosphere with the acetone treated with
KMnO4 and distilled prior to use. The EH-MO calculations
were performed using the program CACAO, version 4.0,
developed by Meally and Proserpio33 and standard atomic
parameters.
The complex [trans-PtHCl(PPh3)2]35 and the alkynes 2-ethy-
nylpyridine,36 2,6-bis(ethynyl)pyridine,37 1,4-bis(ethynyl)ben-
zene,37 and (4-ethynyl)phenylamine37 were prepared by litera-
ture methods. Nonadiyne, 1,1-diphenyl-2-propynol, and NEt2H
were used as received.
Syn th esis of [tr a n s-P tH(CtCC5H4N-2)(P P h 3)2] (1). A
solution of [trans-PtHCl(PPh3)2] (0.40 g, 0.53 mmol) in CHCl3
(10 mL) was treated with 0.30 mL of 2-ethynylpyridine (3.05
mmol) and 0.5 mL of NEt2H. After the mixture was refluxed
for 30 min, it was concentrated to small volume. By addition
of methanol (20 mL) and cooling for ∼12 h, complex 1
precipitated as a white microcrystalline solid. Yield: 74%.
Data for 1 are as follows. Anal. Calcd for C43H35NP2Pt: C,
62.77; H, 4.28; N, 1.70. Found: C, 62.28; H, 3.87; N, 1.73. MS:
m/z 823 [M + H]+ 35%; 719 [Pt(PPh3)2]+ 100%. IR (cm-1): ν-
Syn t h esis of [tr a n s-P t H {CtCC6H 4NH 2-4}(P P h 3)2]‚3/
4CHCl3 (3‚3/4CHCl3). The complex 3‚3/4CHCl3 was prepared
as a yellow solid as described for complex 1, but starting from
0.48 g (0.63 mmol) of [trans-PtHCl(PPh3)2], 0.20 g (1.71 mmol)
of (4-ethynyl)phenylamine, and 1 mL of NEt2H. The mixture
was refluxed for 10 min. Yield: 79%.
Data for 3‚3/4CHCl3 are as follows. Anal. Calcd for C44H37
-
NP2Pt‚3/4CHCl3: C, 58.02; H, 4.11; N, 1.51. Found: C, 57.82;
H, 4.02; N, 1.65. MS: m/z 836 [M]+ 8%; 719 [Pt(PPh3)2]+ 100%.
IR (cm-1): ν(CtC) 2114 (s); ν(Pt-H) 2073 (m). 1H NMR
(CDCl3, δ; J in Hz): 7.71 (m, o-H, Ph, PPh3); 7.36 (m, m-H
and p-H, Ph, PPh3); 6.36 (AB, J H-H ) 8.35, νA ) 6.42, νB
)
2
1
6.30); 3.44 (s br, NH2); -6.27 (t, J P-H ) 15.3, J Pt-H ) 644,
Pt-H). 13C NMR (CDCl3, δ; J in Hz): 143.18 (s, C4); 134.67(t,
1
2J P-C ) 6.6, o-C, Ph, PPh3); 133.40 (t, J P-C + 3J P-C ) 56, i-C,
Ph, PPh3); 132.21 (s, 4J Pt-C ≈10, C2); 130.03 (s, p-C, Ph, PPh3);
3
127.95 (t, J P-C ) 5.2, m-C, Ph, PPh3); 119.50 (s, C1); 114.28
(s, C3); CR and Câ are not observed. 31P NMR (CDCl3, δ; J in
Hz): 27.34 (s, 1J Pt-P ) 2931). The presence of CHCl3 has been
confirmed by 1H NMR in acetone-d6 (δ 8.02) and C6D6 (δ 6.15).
Syn th esis of [tr a n s-P tH{CtC(4-CtCH)C6H4}(P P h 3)2]
(4). A solution of [trans-PtHCl(PPh3)2] (0.40 g, 0.53 mmol) in
CHCl3 (10 mL) was treated with 0.13 g of 1,4-bis(ethynyl)-
benzene (1.71 mmol) and 1 mL of NEt2H, and the mixture was
refluxed for 15 min. Evaporation to dryness of the mixture
and addition of cold methanol (∼5 mL) afforded the precipita-
tion of a pale orange solid (0.414 g), which was identified (1H
and 31P{1H} NMR) as a mixture of complexes 4 and 8 in a 4:1
molar proportion. Recrystallization of the solid in acetone/
MeOH yielded complex 4 as an orange solid. Yield: 65%.
Data for 4 are as follows. Anal. Calcd for C46H36P2Pt: C,
65.32; H, 4.29. Found: C, 65.22; H, 4.59. MS: m/z 845 [M]+
8%; 719 [Pt(PPh3)2]+ 100%. IR (cm-1): ν(CtC) 2099 (s); ν(Pt-
1
H) 2031 (m). H NMR (CDCl3, δ; J in Hz): 7.72 (m, o-H, Ph,
PPh3); 7.38 (m, m-H and p-H, Ph, PPh3); 7.13 (d, J H-H ) 8.1);
2
6.50 (d, J H-H ) 8.1); 3.04 (s, CtCH); -6.11 (t, J P-H ) 14.9;
1J Pt-H ) 651, Pt-H). 13C NMR (CDCl3, δ; J in Hz): 134.57 (s
br, o-C, Ph, PPh3); 133.06 (t, 1J P-C + 3J P-C ) 55, i-C, Ph, PPh3);
(35) Bailar, J . C.; Itatani, H. Inorg. Chem. 1965, 4, 1618.
(36) Ames, D. E.; Bull, D.; Takundwa, C. Synthesis 1981, 364.
(37) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N.
Synthesis 1980, 627.
3
131.02 (s, C3); 130.89 (s, J Pt-C ) 8.5, C2); 130.16 (s, p-C, Ph,
PPh3); 129.59 (s, 2J Pt-C ) 23, C1); 128.00 (s br, m-C, Ph, PPh3);

Hydride-Alkynyl Platinum(II) Complexes
Organometallics, Vol. 19, No. 21, 2000 4395
7.6, J P-Ccis ) 5.8, CPh2OH). 31P NMR (CDCl3, δ; J in Hz):
26.88 (d, J Pt-P ) 3552, J P-P ) 27.5); 24.92 (d, J Pt-P ) 3503,
2J P-P ) 27.5). Acetylenic C resonances for HCtCCPh2OH
(CDCl3, δ; J in Hz): 75.58, 75.51.
117.64 (s, C4); 113.80 (s, 2J Pt-C ) 236, Câ); CR is not observed;
3
â
84.41 (s, Câ, CâtCRH); 79.91 (s, CR, CâtCRH). 31P NMR (CDCl3,
1
2
1
1
δ; J in Hz): 27.60 (s, J Pt-P ) 2914).
Syn th esis of [tr a n s-P tH{CtC(CH2)5CtCH}(P P h 3)2] (5).
Complex 5 was prepared as a white solid following a procedure
identical with that described for 1: 0.50 g (0.66 mmol) of [trans-
PtHCl(PPh3)2], 1 mL (6.65 mmol) of nonadiyne, and 1 mL of
NEt2H were used with a refluxing time of 2 h. Yield: 72%.
Data for 5 are as follows. Anal. Calcd for C45H42P2Pt: C,
64.35; H, 5.00. Found: C, 64.23; H, 4.81. MS: m/z 839 [M]+
5%; 719 [Pt(PPh3)2]+ 100%. IR (cm-1): ν(CtC) 2121 (m); ν-
Syn th esis of [tr a n s,tr a n s-(P P h 3)2HP t{µ-σ:σ-(CtC)2C5-
H3N-2,6}P tH(P P h 3)2] (7). An equimolecular mixture of [trans-
PtHCl(PPh3)2] (0.33 g, 0.44 mmol) and complex 2 (0.37 g, 0.44
mmol) was refluxed with 2 mL of NEt2H, in 20 mL of CHCl3,
for 1 h. By concentration to small volume (ca. 5 mL) and
addition of 20 mL of MeOH, complex 7 precipitates as an
orange solid. Yield: 72%.
Complex 7 was alternatively obtained by refluxing [trans-
PtHCl(PPh3)2] (0.4 g, 0.53 mmol) and 2,6-bis(ethynyl)pyridine
(0.07 g, 0.55 mmol) with 0.5 mL of NEt2H, in 20 mL of CHCl3,
for 90 min. Concentration to small volume (ca. 5 mL) and
addition of 20 mL of MeOH yielded 0.147 g of a beige solid,
which was identified (31P NMR) as a mixture of 2 and 7 (molar
ratio 1:1.4, respectively). Recrystallization of the mixture in
CHCl3/MeOH gave 0.085 g of complex 7. Yield: 20.5% (based
on Pt).
1
(Pt-H) 2034 (m). H NMR (CDCl3, δ; J in Hz): 7.70 (m, o-H,
Ph, PPh3); 7.36 (m, m-H and p-H, Ph, PPh3); 2.01 (dt, J H-H
)
13.42, J H-H ) 1.47, H7); 1.89 (br, CtCH); 1.83 (t, J H-H ) 12.08,
H3); 1.34 (t, J H-H ) 14.04, H6); 1.08 (m, H,4 H5); -6.54 (t, 2J P-H
1
) 15.5; J Pt-H ) 640, Pt-H). 13C NMR (CDCl3, δ; J in Hz):
1
3
134.70 (s br, o-C, Ph, PPh3); 133.57 (t, J P-C + J P-C ) 56.2,
i-C, Ph, PPh3); 129.96 (s, p-C, Ph, PPh3); 127.81 (s br, m-C,
2
Ph, PPh3); 113.96 (s, J Pt-C ) 236, Câ); 107.17 (m, CR); 85.01
â
4
(s, Câ, CâtCRH); 67.86 (s, CR, CâtCRH); 29.47 (s, J Pt-C ∼9,
C4); 28.32 (s, C5 or C6); 28.20 (s, C5 or C6); 21.46 (s, J Pt-C
)
Data for 7 (by using the sample obtained by the first
synthetic method). Anal. Calcd for C81H65NP4Pt2: C, 62.11; H,
4.18; N, 0.89. Found: C, 62.06; H, 3.66; N, 1.33. MS: m/z 1566
[M + H]+ 11%; 377 [PtPPh2 - 1]+ 100%. IR (cm-1): ν(CtC)
2099 (s); ν(Pt-H) ∼2041 (sh). 1H NMR (CDCl3, δ; J in Hz):
7.72 (m, o-H, Ph, PPh3); 7.31 (m, m-H and p-H, Ph, PPh3); 6.85
(t, J H-H ) 7, H4); 6.08 (d, J H-H ) 7, H3); -6.30 (t, 2J P-H ) 15.3;
1J Pt-H ) 646, Pt-H). 13C NMR (CDCl3, δ; J in Hz): 146.10 (s,
3
19, C3); 18.30 (s, C7). 1H and 13C{1H} NMR spectra were
1
1
assigned on the basis on H-1H COSY and H-13C correlation
NMR spectra. 31P NMR (CDCl3, δ; J in Hz): 26.91 (s, 1J Pt-P
)
2948).
Rea ction of [tr a n s-P tHCl(P P h 3)2] w ith HCtCCP h 2OH.
1,1-Diphenyl-2-propynol (0.4 g, 1.92 mmol) and 0.5 mL of
NEt2H were added to a solution of 0.4 g (0.53 mmol) of [trans-
PtHCl(PPh3)2] in 20 mL of CHCl3. The mixture was refluxed
for 3.5 h, evaporated to dryness, and treated with 15 mL of
MeOH, causing the precipitation of a white solid which was
identified (1H and 31P NMR) as a mixture of the isomers [trans-
PtH(CtCCPh2OH)(PPh3)2] (6a ) and [Pt(η2-HCtCCPh2OH)-
(PPh3)2] (6b) in a 2:1 molar proportion. Yield: 35% (based on
Pt). (Anal. Calcd for C51H42OP2Pt: C, 66.01; H, 4.56. Found:
C, 65.57; H, 4.89. MS: m/z [M+] 927 5%). Further attempts to
separate completely both complexes by standard recrystalli-
zation methods were unsuccessful.
Complex 6b can also be obtained pure as a pale yellow
microcrystalline solid by literature methods10d or reacting the
equimolecular amount of [Pt(η2-C2H4)(PPh3)2] (0.2 g, 0.27
mmol) and 1,1-diphenyl-2-propynol (0.056 g, 0.27 mmol) in 10
mL of acetone. Evaporation of the reaction mixture to ca. 5
mL causes the precipitation of 6b in 60% yield.
2
3J Pt-C ) 22.4, C2); 133.43 (s, C4); 134.62 (t, J P-C ) 6.2, o-C,
1
Ph, PPh3); 133.23 (t, J P-C
+
3J P-C ) 56.4, i-C, Ph, PPh3);
130.03 (s, p-C, Ph, PPh3); 127.98 (s br, m-C, Ph, PPh3); 124.84
(t, J P-C ) 10.6, CR); 122.03 (s, C3); 115.90 (s, J Pt-C ) 235,
2
2
Câ). 31P NMR (CDCl3, δ; J in Hz): 26.33 (s, J Pt-P ) â2919).
R
1
Syn th esis of [tr a n s,tr a n s-(P P h 3)2HP t{µ-σ:σ-(CtC)2C6H4-
1,4}P tH(P P h 3)2] (8). Complex 8 was prepared as a pale yellow
solid following a procedure identical with that described for
7: 0.21 g (0.28 mmol) of [trans-PtHCl(PPh3)2], 0.24 g (0.28
mmol) of 4, and 1 mL of NEt2H were used with a refluxing
time of 3.5 h. Yield: 71%.
Complex 8 was alternatively obtained by refluxing [trans-
PtHCl(PPh3)2] (0.4 g, 0.53 mmol) and 1,4-bis(ethynyl)benzene
(0.033 g, 0.26 mmol) with 0.5 mL of NEt2H, in 20 mL of CHCl3,
for 75 min. Concentration to small volume (ca. 5 mL) and
addition of 20 mL of MeOH yielded 0.212 g of a beige solid,
which was identified (31P NMR) as a mixture of 4, 8, and [{-
(PPh3)2Pt}2{µ-η2:η2-(CtCH)2C6H4-1,4}] (9) (molar ratio ∼1:4.1:
1.6, respectively). Recrystallization of the mixture in CH2Cl2/
acetone rendered 0.075 g of complex 8. Yield: 18% (based on
Pt).
Complex 6a was spectroscopically characterized from the
mixture of 6a ,b. IR (cm-1): ν(CtC) 2106 (m); v(Pt-H) 2047
(m). 1H NMR (CDCl3, δ; J in Hz): 7.65 (m, o-H, Ph, PPh3);
7.30 (m, m-H and p-H, Ph, PPh3); 7.10, 7.05 (m, Ph, CPh2-
2
1
OH); 1.37 (s, OH); -6.35 (t, J P-H ) 14.6; J Pt-H ) 666, Pt-
H). 13C NMR (CDCl3, δ; J in Hz): 147.45 (s, i-C, Ph, CPh2OH);
134.63 (s br, o-C, Ph, PPh3); 133.06 (t, 1J P-C + 3J P-C ) 56, i-C,
Ph, PPh3); 130.20 (s, p-C, Ph, PPh3); 128.07 (s br, m-C, Ph,
PPh3); 127.30 (s, Ph, CPh2OH); 126.21 (s, Ph, CPh2OH); 125.93
Data for 8 are as follows (by using the sample obtained by
the first synthetic method). Anal. Calcd for C82H66P4Pt2: C,
62.91; H, 4.25. Found: C, 62.34; H, 3.98. MS: m/z 1565 [M +
H]+ 2%; 719 [Pt(PPh3)2]+ 100%. IR (cm-1): ν(CtC) 2102 (s);
ν(Pt-H) 2038 (m). 1H NMR (CDCl3, δ; J in Hz): 7.69 (m, o-H,
Ph, PPh3); 7.34 (m, m-H and p-H, Ph, PPh3); 6.21 (s, H2); -6.26
(t, 2J P-H ) 15.4; 1J Pt-H ) 646, Pt-H). 13C NMR (CDCl3, δ; J in
2
(s, p-C, Ph, CPh2OH); 115.47 (s, J Pt-C ) 231.4, Câ); CR is not
â
observed; 75.23 (s, J Pt-C ≈ 20, CPh2OH). 31P NMR (CDCl3, δ;
3
1
J in Hz): 29.37 (s, J Pt-P ) 2907).
2
1
Hz): 134.65 (t, J P-C ) 6.6, o-C, Ph, PPh3); 133.32 (t, J P-C
+
Data for complex 6b are as follows. Anal. Calcd for C51H42
-
3J P-C ) 56, i-C, Ph, PPh3); 130.05 (s, p-C, Ph, PPh3 and
probably C2); 127.97 (t, 3J P-C ) 5.2, m-C, Ph, PPh3); 124.92 (s,
3J Pt-C ) 22, C1); 123.13 (t, 2J P-C ) 11.9, CR); 115.29 (s, 2J Pt-C
OP2Pt: C, 66.01; H, 4.56. Found: C, 66.03; H, 4.51. IR (cm-1):
ν(CtC) 1692 (s). 1H NMR (CDCl3, δ; J in Hz): 7.44, 7.18, 6.98
2
3
(m, Ph, PPh3 and CPh2OH); 6.46 (dd, J Pt-H ) 57.7, J Ptrans-H
R
â
) 235.5, Câ). 31P NMR (CDCl3, δ; J in Hz): 27.23 (s, J Pt-P
)
1
3
) 22.7, J Pcis-H ) 9.6, CtCH); 2.11 (s, OH). 13C NMR (CDCl3,
δ; J in Hz): 147.98 (d, 4J P-C ) 1.2, 3J Pt-C ) 13.2, i-C, Ph, CPh2-
2929).
Syn th esis of [{(P P h 3)2P t}2{µ-η2:η2-(CtCH)2C6H4-1,4}]
(9). Complex 9 was prepared, as described for 6b, by treating
a suspension of 0.3 g (0.4 mmol) of [Pt(η2-C2H4)(PPh3)2] in 10
mL of acetone with 0.025 g (0.2 mmol) of 1,4-bis(ethynyl)-
benzene. The mixture was stirred for 10 min, giving a
suspension, which was evaporated to ca. 5 mL and filtered to
yield complex 9 as a pale orange solid. Yield: 83%.
1
3
2
OH); 137.08 (dd, J P-C ) 41.4, J P-C ) 3.2, J Pt-C ) 25, i-C,
Ph, PPh3); 136.17 (dd, 1J P-C ) 42.6, 3J P-C ) 2.5, 2J Pt-C ) 29.3,
2
3
i-C, Ph, PPh3); 134.01 (d, J P-C ) 13.4, J Pt-C ) 20.8, o-C, Ph,
2
3
PPh3); 133.86 (d, J P-C ) 12.9, J Pt-C ) 19.8, o-C, Ph, PPh3);
4
4
129.3 (d, J P-C ) 1.4, p-C, Ph, PPh3); 129.0 (d, J P-C ) 1.8,
3
p-C, Ph, PPh3); 127.77 (d, J P-C ) 9.7, m-C, Ph, PPh3); 127.59
(d, 3J P-C ) 9.9, m-C, Ph, PPh3); 127.47 (s, Ph, CPh2OH); 126.57
(s, Ph, CPh2OH); 126.12 (s, p-C, Ph, CPh2OH); 113.20 (dd,
Data for 9 are as follows. Anal. Calcd for C82H66P4Pt2: C,
62.91; H, 4.25. Found: C, 62.94; H, 4.29. MS (ES+): m/z 1566
2J C-Ptrans ) 62.5, 2J P-Ccis ) 5.5, CR or Câ); 77.98 (dd, 3J C-Ptrans
)

4396 Organometallics, Vol. 19, No. 21, 2000
Ara et al.
[M + 2H]+ 1%; 719 [Pt(PPh3)2]+ 100%. IR (cm-1): ν(CtC) 1688
(m). 1H NMR (CDCl3, δ; J in Hz): 7.29, 7.18, 7.12, 7.00 (m,
PPh3 and CtCH); 6.59 (s, C6H4). 13C NMR (CDCl3, δ; J in
Ta ble 5. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
P a r a m eter s for 1 a n d 6b
1
6b
1
3
2
Hz): 136.79 (dd, J P-C ) 41.2, J P-C ) 3.0, J Pt-C ) 25.3, i-C,
empirical formula
fw
C
43H35NP2Pt
C51H42OP2Pt
927.88
Ph, PPh3); 136.40 (dd, 1J P-C ) 41.9, 3J P-C ) 2.5, 2J Pt-C ) 28.9,
822.75
2
3
i-C, Ph, PPh3); 134.02 (d, J P-C ) 13.7, J Pt-C ) 20.45, o-C,
Ph, PPh3); 133.78 (d, 2J P-C ) 13.1, 3J Pt-C ) 19.2, o-C, Ph, PPh3);
130.83 (m br, C6H4); 128.9 (s br, p-C, Ph, PPh3); 127.58 (d, 3J P-C
temp (K)
wavelength (Å)
cryst syst
space group
unit cell dimens
a (Å)
173(2)
200(2)
0.710 73
monoclinic
P21/n
0.710 73
monoclinic
P21/n
3
) 9.4, m-C, Ph, PPh3); 127.51 (d, J P-C ) 9.7, m-C, Ph, PPh3);
2
2
114.85 (overlaping of two dd, J C-Ptrans ≈ 63, J C-Pcis ≈ 6.5,
1J Pt-C ≈ 260, CR and Câ). 31P NMR (CDCl3, δ; J in Hz): 30.76
(d, 1J Pt-P ) 3535.5, 2J P-P ) 33.9); 26.22 (d, 1J Pt-P ) 3427, 2J P-P
) 33.9). Acetylenic C resonances for 1,4-bis(ethynyl)benzene
(CDCl3, δ; J in Hz): 79.07, 82.98.
9.769(1)
19.182(1)
18.487(1)
90
98.45(1)
90
9.255(1)
18.010(2)
24.330(3)
90
94.60(1)
90
4042.3(8)
4
1.525
b (Å)
c (Å)
R (deg)
â (deg)
Syn th esis of [{tr a n s-(P P h 3)2H-P t-CtCRCtCH}P t-
(P P h 3)2] (R ) (CH2)5 (10), C5H3N-2,6 (11), C6H4-1,4 (12)).
Solutions of [trans-PtH(CtCR)(PPh3)2] (R ) (CH2)5CtCH (5),
0.137 g (0.16 mmol); R ) (6-CtCH)C5H3N-2 (2), 0.052 g (0.06
mmol); R ) (4-CtCH)C6H4 (4), 0.1 g (0.12 mmol)) in 10 mL of
acetone were treated with [Pt(η2-C2H4)(PPh3)2] (0.122 g (0.16
mmol) for 5; 0.046 g (0.06 mmol) for 2; 0.088 g (0.12 mmol) for
4), and the mixtures were stirred for 10 min. After this time,
the resulting solutions were evaporated to dryness and the
residues treated with cold EtOH (∼5 mL), yielding complexes
10 (87%) and 11 (73%) as beige solids. For 12, evaporation of
the acetone solution to ca. 5 mL caused the precipitation of
this complex as a yellow solid (65%).
γ (deg)
V (Å3)
3426.6(4)
4
Z
calcd density (Mg/m3) 1.595
abs coeff (mm-1
F(000)
)
4.221
1632
3.589
1856
cryst size
0.50 × 0.15 × 0.10 0.74 × 0.50 × 0.26
θ range for data
collecn (deg)
index ranges
1.54-30.47
2.02-25.00
0 e h e 13
0 e k e 27
-26 e l e 26
10 098
-11 e h e 0
-21 e k e 1
-28 e l e 28
7816
no. of rflns collected
no. of indep rflns
10 098 (R(int) )
7038 (R(int) )
0.05)
0.0204)
refinement method
full-matrix least-squares on F2
Data for complex 10 are as follows. Anal. Calcd for C81H72P4-
Pt2: C, 62.38; H, 4.65. Found: C, 62.55; H, 4.32. MS (ES+,
ionized with Ag+): m/z 1666 [M + Ag]+ 12%, 718 [Pt(PPh3)2 -
H]+ 100%. IR (cm-1): ν(CtC) 2124 (m), 1718 (m); ν(Pt-H)
2037 (m). 1H NMR (CDCl3, δ; J in Hz): 7.68, 7.31, 7.10 (m,
PPh3); 6.40 (dd, 3J Ptrans-H ) 20.7, 3J Pcis-H ) 11.2); 2.24 (m, H7);
1.75 (m, H3); 1.29, 1.21 (m, H5, H6); 0.95 (m, H4); -6.53 (t, 2J P-H
no. of data/restraints/ 10 098/0/428
params
6568/0/496
goodness of fit on F2 a 1.019
1.061
final R indices
R1 ) 0.0564,
wR2 ) 0.0911
R1 ) 0.1341,
wR2 ) 0.1113
1.166 and -1.523
R1 ) 0.0323,
wR2 ) 0.0560
R1 ) 0.0572,
wR2 ) 0.0627
1.114 and -0.555
(I > 2σ(I))b
R indices (all data)
1
) 15.4; J Pt-H ) 639.5, Pt-H); (based on 1H-1H COSY
largest diff peak
and hole (e/Å3)
spectrum). 13C NMR (CDCl3, δ; J in Hz): at -50 °C, 136.32
1
3
2
(dt, overlaping of two dd, J P-C ≈ 41, J P-C ≈ 3, J Pt-C ≈ 30,
a
2
Goodness of fit ) [∑w(Fo - Fc2)2/(nobservns - nparams)]1/2; w )
i-C, Ph, (η2-CtCH)Pt(PPh3)2); 134.38 (t, J P-C ) 6.6, o-C, Ph,
2
[σ2(Fo) + (g1P)2 + g2P]-1; P ) [max(Fo2; 0) + 2Fc2]/3. R1 ) ∑(|Fo|
b
PtH(PPh3)2); 133.49 (d, J P-C ) 13.05, o-C, Ph, (η2-CtCH)Pt-
2
- |Fc|)/∑|Fo|; wR2 ) [∑w(Fo - Fc2)2/∑w(Fc2)2]1/2
.
2
(PPh3)2); 133.43 (d, 2J P-C ) 13.7, o-C, Ph, (η2-CtCH)Pt(PPh3)2);
1
3
132.74 (t, J P-C + J P-C ) 58.6, i-C, Ph, PtH(PPh3)2); 129.93
(s, p-C, Ph, PtH(PPh3)2); 128.83 (s, p-C, Ph, (η2-CtCH)Pt-
(PPh3)2); 128.77 (s, p-C, Ph, (η2-CtCH)Pt(PPh3)2); 127.56 (m,
m-C, Ph, (η2-CtCH)Pt(PPh3)2 and PtH(PPh3)2); 114.46 (s,
2
1
2
1J Pt-P ) 3535, J P-P ) 34.1); 26.46 (d, J Pt-P ) 3527, J P-P
)
1
34.1); 26.30 (s, J Pt-P ) 2918).
Data for complex 12 are as follows. Anal. Calcd for C82H66P4-
Pt2: C, 62.91; H, 4.25. Found: C, 62.48; H, 4.10. MS: m/z 1565
[M + H]+ 3%; 719 [Pt(PPh3)2]+ 100%. IR (cm-1): ν(CtC) 2103
2J Pt-C ) 235.4, Câ); 106.5 (t, J P-C ) 11.4, CR); 104.55 (dm,
2
â
R
probably overlapping of two dd, J C-Ptrans ≈ 67, CRtCâH, C8
2
1
(s), 1678 (m); ν(Pt-H) 2050 (s). H NMR (CDCl3, δ; J in Hz):
and C9); 31.50 (d, J C-Ptrans ) 5.8, J C-Pcis) 1.0, J Pt-C ) 42.8,
3
3
2
7.67, 7.32, 7.11 (m, PPh3 and CtCH); 6.69 (d, J H-H ) 6.5);
C7); 29.58 (s br), 28.99 (s br), 27.72 (m), 21.44 (s br) (CH2). 31
P
2
6.12 (d, J H-H ) 6.5); -6.24 (t, J P-H ) 15.4; 1J Pt-H ) 645, Pt-
NMR (CDCl3, δ; J in Hz): 31.33 (d, 1J Pt-P ) 3599, 2J P-P ) 31.3);
1
H). 13C NMR (CDCl3, δ; J in Hz): 136.94 (dd, J P-C ) 41.2,
28.44 (d, 1J Pt-P ) 3425, 2J P-P ) 31.3); 26.79 (s, 1J Pt-P ) 2965).
1
3J P-C ) 3.2, i-C, Ph, (η2-CtCH)Pt(PPh3)2); 136.43 (dd, J P-C
3
) 41.6, J P-C ) 2.6, i-C, Ph, (η2-CtCH)Pt(PPh3)2); 134.61 (t,
Data for complex 11 are as follows. Anal. Calcd for C81H65
-
2J P-C ) 6.3, o-C, Ph, PtH(PPh3)2); 134.11 (d, 2J P-C ) 13.5, o-C,
NP4Pt2: C, 62.24; H, 4.23; N 0.91. Found: C, 62.47; H, 4.28,
N, 0.95. MS (ES+, in the range 1500-1600): m/z 1566 [M +
1]+ 100%. IR (cm-1): ν(CtC) 2102 (m), 1685 (s); ν(Pt-H) 2040
2
Ph, (η2-CtCH)Pt(PPh3)2); 133.83 (d, J P-C ) 13.15, o-C, Ph,
1
3
(η2-CtCH)Pt(PPh3)2); 133.2 (t, J P-C + J P-C ) 55.1, i-C, Ph,
PtH(PPh3)2); 130.05 (s, p-C, Ph, PtH(PPh3)2); 128.92 (overlap-
ping of two singlets, p-C, Ph, (η2-CtCH)Pt(PPh3)2); 127.95 (t,
3J P-C ) 4.8, m-C, Ph, PtH(PPh3)2); 127.64 (d, 3J P-C ) 7.9, m-C,
Ph, (η2-CtCH)Pt(PPh3)2); 127.53 (d, 3J P-C ) 9.5, m-C, Ph, (η2-
CtCH)Pt(PPh3)2); 115.18 (s, Câ); 113.92 (dm, probably over-
1
(sh). H NMR (CDCl3, δ; J in Hz): 7.67, 7.26, 7.15, 7.08, 6.97
(m, PPh3 and CtCH); 6.50 (t, J H-H ) 7.8, H4); 6.03 (d, J H-H
)
8.5), 6.00 (d, J H-H ) 8.3) (H3, H5); -6.36 (t, 2J P-H ) 15.2; 1J Pt-H
) 644.1, Pt-H). 13C NMR (CDCl3, δ; J in Hz): at -50 °C,
149.54 (m, C6); 145.79 (s, C2); 135.55 (dm, overlapping of two
dd, i-C, 1J P-C ≈ 43, 2J Pt-C ≈ 25, i-C, Ph, (η2-CtCH)Pt(PPh3)2);
2
lapping of two dd, J C-Ptrans ≈ 64, CRtCâH); due to the low
2
134.32 (t, J P-C ) 6.6, o-C, Ph, PtH(PPh3)2); 133.59 (m,
solubility of the complex carbon atoms of the C6H4 group
overlapping of two d, o-C, Ph, (η2-CtCH)Pt(PPh3)2); 132.38 (t,
cannot be unequivocally assigned (130.67 (m), 130.45 (m),
3
1J P-C + J P-C ) 57, i-C, Ph, PtH(PPh3)2); 130.10 (s, p-C, Ph,
1
126.40 (s)). 31P NMR (CDCl3, δ; J in Hz): 30.94 (d, J Pt-P
)
)
PtH(PPh3)2); 128.88 (s br, overlapping of two s, p-C, Ph, (η2-
CtCH)Pt(PPh3)2); 127.89 (t, 3J P-C ) 5.1, m-C, Ph, PtH(PPh3)2);
3543, 2J P-P ) 34.2); 27.15 (s, 1J Pt-P ) 2927); 26.20 (d, 1J Pt-P
2
3425, J P-P ) 34.2).
3
127.46 (d, J P-C ) 9.3, m-C, Ph, (η2-CtCH)Pt(PPh3)2); 127.39
X-r a y Cr ysta llogr a p h ic An a lysis of 1. Table 5 reports
details of the structure analyses for 1 and 6b.
3
(d, J P-C ) 9.7, m-C, Ph, (η2-CtCH)Pt(PPh3)2); 122.66 (dm,
2
probably overlapping of two dd, J C-Ptrans ≈ 85, CRtCâH);
A colorless rod-shaped crystal of 1, obtained by slow diffu-
sion of hexane into a tetrahydrofuran solution of this complex
at -30 °C, was fixed with high-vacuum grease on top of a glass
114.72 (s, Câ); carbon atoms C3, C4 and C5 of the pyridyl group
cannot be assigned. 31P NMR (CDCl3, δ; J in Hz): 30.17 (d,

Hydride-Alkynyl Platinum(II) Complexes
Organometallics, Vol. 19, No. 21, 2000 4397
fiber. The diffraction measurements were made at 173 K with
a NONIUS κCCD instrument, using graphite-monochromated
Mo KR radiation. No crystal decay was observed over the data
collection period. The structure was solved by direct methods
and refined using full-matrix least-squares refinement on F2
with the SHELXL-97 program.38 All non-hydrogen atoms and
H(1) were located in succeeding difference Fourier syntheses
and refined with anisotropic thermal parameters. All hydrogen
atoms were constrained to idealized geometries and assigned
isotropic displacement parameters 1.2 times the Uiso value of
their carbon attached for the aromatic hydrogens. Final
difference electron density maps showed no features outside
the range 1.166 to -1.523 e/Å3.
collection. An empirical absorption correction based on ψ scans
was applied (12 reflections, maximum and minimum trans-
mission factors 0.878, 0.588). The structure was solved by the
Patterson method, which revealed the position of the platinum
atom. All non-hydrogen atoms were located in succeeding
difference Fourier syntheses and refined with anisotropic
thermal parameters. Hydrogen atoms were added at calculated
positions and assigned isotropic displacement parameters
equal to 1.2 times the Uiso value of their respective parent
carbon atoms. There is a peak of electron density higher than
1 e/Å3 (1.11 e/Å3) in the final map, but it is located very close
to the platinum atom and has no chemical meaning.
X-r a y Cr yst a llogr a p h ic An a lysis of 6b . A pale yellow
trigonal-prism-shaped crystal of 6b, obtained by slow diffusion
of hexane into a CHCl3 solution of the crude mixture of 6a ,b
at -30 °C, was fixed with epoxy on top of a glass fiber and
transferred to the cold stream of the low-temperature device
of a Siemens P4 automated four-circle diffractometer. Cell
constants were calculated from 50 well centered reflections
with 2θ angles ranging from 24 to 26°. Data were collected at
200 K by the ω method. Three check reflections measured at
regular intervals showed no loss of intensity at the end of data
Ack n ow led gm en t. We thank the Direccio´n General
de Ensen˜anza Superior (Spain, Project PB 98-1595-C02-
01,02) and the Universidad de La Rioja (Project API-
99/B16) for their financial support.
Su p p or tin g In for m a tion Ava ila ble: Tables of all atomic
positional and equivalent isotropic displacement parameters,
anisotropic displacement parameters, all bond distances and
bond angles, and hydrogen coordinates and isotropic displace-
ment parameters for the crystal structures of complexes 1 and
6b. This material is available free of charge via the Internet
at http://pubs.acs.org.
(38) Sheldrick, G. M. SHELXL-97: Program for Crystal Structure
Determination from Diffraction Data; University of Go¨ttingen, Go¨t-
tingen, Germany, 1997.
OM000143U